Proper Mass Of Tonearm for MC Cart

Two years have passed since I rediscovered vinyl. I have a MM Maestro, and am considering a middle range MC cartridge. It's been suggested that with some MC carts, a tonearm of high mass is needed for proper tracking etc. I will be shopping for a new TT and MC cart with a budget of $3-6K for both. My ARC PH-7 phono stage only goes down to 100 ohms, and I'm happy with it. I was entertaining the new Rega P-8 with the Apheta cart, but reviews have stated this cart "likes" 50 ohms and below and some say is a little grainy. Maybe just the Rega 8 without the Apheta? I'm not leaning toward any particular brand-just noticed the new Rega. Any suggestions?
The title of your post and the question you seem to be asking do not match so well. What is it you really want "suggestions" about? MCs are typically low in compliance. Such cartridges generally sound best in mid- to high-mass tonearms. There is a formula to relate compliance to tonearm effective mass, available on Vinyl Engine, but it's not gospel. Sometimes you can bend the rule and get good results. You might want to do some reading on VE and on Vinyl Asylum.
Yes-you are correct. I kinda went off on a tangent. I was inquiring about tonearm mass, but thought I would ask for recommendations of a TT/Cart combo. I had always thought you find a TT you like and a cartridge you can afford. I was ignorant in knowing one needs to match a cart with a specific tonearm; then there's the capacitance of your interconnects etc. The more I learn, the more I find out how much I do not know.
The more you play with this stuff, the more you find that rules are made to be broken, so don't sweat it too much.